Why we always measuring voltage and curent between two points.?
Voltage is defined as the potential difference between two points, so two points are needed to measure voltage. Current is not measured at two points, since it is defined as the rate of charge passing through one path (that has two ends). So you measure it by breaking that path and inserting the measuring device in series with that path. This takes two connections, but they are made to the two sides of the single point that was broken to allow the meter to be inserted in the current path. There are some meters that do not require this break, because they measure the strength of the magnetic field produced by current passing through a path. These have a probe that encircles the current conductor without any break or connection made to the circuit.
